Universal receiver without transformer



June 13, 1939. P; KAPTEYN 2,162,350

UNIVERSAL RECEIVER W ITHOUT TRANSFORMER Filed Aug. 3, 1935 Patented June13, 1939 PATENT OFFICE UNIVERSAL RECEIVER WITHOUT TRANSFORMER PaulKapteyn, Berlin, Germany, assignor to Radioaktiengesellschaft D. S.Loewe, Berlin-Steglitz, Germany, a corporation of Germany ApplicationAugust 3,

1933, Serial No. 683,423

In Germany August 4, 1932 8 Claims.

In the case of universal receivers, which after slight alteration in theconnections require to be capable of use in connection with all supplypotentials and all kinds of current, various aspects 5 must be takeninto consideration, which constitute subject matter of the presentinvention.

Since receivers of this nature should still perate even in the case ofvery low supply potentials (for example, 110 volts D. C.), the dimen- 1osions of the house-circuit connection portions above all require to besuch that an excessive loss of potential is unable to take place in thesteadying resistances. It is, therefore, desirable to employ relativelysmall steadying resistances,

' and to obtain the requisite steadying action by the use of relativelylarge condensers. For reasons associated with the cost and weight it isadvisable to employ for this purpose electrolytical condensers. Whenusing condensers of this nature, however, there is encountered thedisadvantage that consideration requires to be paid to the poling, asthe condensers in the case of incorrect poling are quickly destroyed.

This danger exists when employing the receiver in connection with,direct current circuits, as it is not to be recognised immediately(above all when using indirectly heated, i. e., relatively slowly heatedtubes) which poling is correct.

To overcome these difficulties, .1 have devised a novel arrangement, atypical example of which is illustrated by the accompanying drawing,which shows a three-tube system adapted for use either with alternatingcurrent (as by direct connection with a house circuit) or with directcurrent.

An antenna system of conventional type, shown at the extreme left,transmits the received impulses to the detector tube I connected in anywell-known or approved manner to the first-stage audio-amplifier tube 2and the second-stage 5 rectifier tube 4 may be excluded from the circuitfor a purpose explained below; ordinarily, the switch 5 is in its lowerposition, so as to include the rectifier tube in the circuit. The anodeof the rectifier tube 4 is connected with a terminal I0, adapted forconnection with one D. C. lead (the positive lead) or one of the A. C.leads, the other D. C. or A. C. lead being connected to a commonterminal 9. Each of the three tubes I, 2, and 3 is shown as having ananode, a grid, and

I a cathode, the three cathodes being connected in series and heatedheaters, indicated below the respective cathodes. These heaters areconnected in series, the righthand heater being connected with theterminal III, while the left-hand heater is connected with the terminal9. The last-mentioned terminal is also connected, through a connectionincluding a condenser, with the lower one of the two contacts adapted tobe engaged by the switch 5, and through another connection said terminal9 is connected with the switch 5, said second connection including anelectrolytic condenser 6, a lamp 1, and a protective resistance 8, thesethree parts being arranged in series. The anode of the tube 3 isconnected with the switch 5 through the resistance 8 and through acondenser shown directly above said tube, and loud-speaker connectionsare indicated from the opposite terminals of said condenser. Throughsuitable connections including a smoothing resistance l2, the switch 5is connected with the anodes of the other two tubes I and 2. These twoanodes are connected, by connections including condensers, with thegrids of the tubes 2 and 3 respectively. The grids of the three tubesare connected, in the manner illustrated, with a device for producinggrid bias, said device comprising the resistances l4, I5, l6 and thecondenser I1. At I3 I have shown a by-pass condenser. Connections for aphonograph pick-up are indicated at 20 and 2|, with a protectivecondenser [9 in one of these connections and a resistance l8 in theother, said resistance being employed to diminish hum.

The following features are of particular importance in securing theresults for which my invention was designed:

1. Upon changing over to direct current care is taken that none of thefitted electrolytic condensers is able to be applied to the supplycircuit in direct fashion, but that in each case the resistance 8 of,for example, 2000 ohms or more is connected in front of the electrolyticcondensers remaining in operation as compared with the supply terminals.Experiments have shown that when using a guard resistance of this natureincorrect poling even if continued for a relatively long period of timehas no detrimental effect on the electrolytic condenser.

2. Since in the case of incorrect poling the insulation. current throughthe electrolytic condenser is considerably greater than in correctpoling, a small lamp 1 (for example, a suitably dimensioned pocket-lampbulb) may be connected in series with the electrolytic condenser 6. Thislights in the case of incorrect poling, and prevents indirectly byfilamentary lengthy operation with poling of an incorrect kind if itsfilament is so selected that the same fuses if heated for a long time(more than (0 hour).

3. Since the total current of the receiver is greater in the case ofincorrect poling, the fuse connected in series with the receiver may beso selected that the same burns out in the case of incorrect poling overa relatively long period.

4. The best ensurity against incorrect poling is constituted by therectifier tube 4 which is connected in series with the electrolyticcondenser, and allows current to pass only in the one direction. Thisrectifier tube necessary for A. C. operation should accordinglypreferably be allowed to remain in the receiver when changing over todirect current.

Further difliculties in connection with universal receivers areencountered as a result of the requisite potential guard, for examplefor talking machine connection such as indicated at 20, 2|, as the:steadying condensers allow alternating current to pass. In this caseseparation of the outwardly leading terminals from the supply circuitmay be obtained either by an intermediate transformer or (and this ischeaper) by suitably connected series resistances such as indicated at18, or condensers such as indicated at H].

In the prior art, one of the sound-box leads is usually applied indirect fashion to the grid, or the anode, of the first low-frequencytube, and is secured to a sufiicient extent against danger of contact bythe series-connected audion combination, or the highly ohmic resistancessit-u ated in the anode circuit (in the case of resistanceamplification), as the current occurring is unable to exceed a valuewhich would be detrimental. The other lead is usually connected with thegrid bias, the cathode or the anode potential of the receiver. Thesepoints owing to the necessary steadying condensers are dangerous totouch. It is, therefore, desirable to connect in this lead resistanceswhich limit the occurring current in the case of contact.

The practical examination of receivers connected in this fashion hasshown. that owing to the high A. C. potentials in the apparatus ahumming noise occurred by reason of capacitative dispersion. This iscaused above all by the fact that the sound-box is connected with thezero point in the apparatus, not in direct fashion, but through themedium of the guard resistance. The dispersion is particularlydisturbing as the same, owing to their capacitative nature, favour quiteparticularly the greatly audible overtones of the supply circuit.

According, therefore, to the invention, there is not employed a guardresistance, but a guard condenser 19, the capacitative resistance ofwhich in the case of 50 cycles is approximately equal to the valuenecessary for limitation of the current. As regards the higherdisturbing irequencies, which above all cause the humming noise, thiscondenser forms practically a shortcircuit, so that the humming noiseoccurring is greatly diminished.

In order to reduce still further the humming noise occurring uponconnection of the soundbox, the reception of humming disturbances isreduced in accordance with the invention by the fact that a distributionof potential is produced by means of the (ohmic) series resistance I8 inthe lead to the grid or the anode. This resistance diminishes at thesame time the amplification for the sound-box amplification, and must,therefore, be selected in such fashion that in the case of fully openedsound regulator the intensity of the sound in the loud-speaker is justsufficient.

In the case of tub-es having high voltage cathodes for universalreceiversv of this nature a humming dispersion also takes place byreason of capacitative coupling of grid and heating connections. This isavoided to a considerable extent in accordance with the invention by theuse of indirectly heated cathodes with double-wound arrangement of thefilament, i. e., cathodes in which the heat requires to be supplied onlyfrom the one side. At the other end of the tube the free end of thefilament there present is preferably screened oif by correspondingconstruction of the nickel jacket.

The elements 6, 1, 8 constitute a steadying filter. The resistancesemployed in the filters are of the order of 1000 ohms, and thecondensers (preferably of the electrolytic type) used in conjunctionwith these resistances have a capacity of more than 6 microfarads, forinstance between 6 and 8 microfarads.

I claim:

1. A universal receiver operable by connection with either alternatingcurrent or direct current mains, said receiver being provided withsmoothing means consisting of ohmic resistances in the order of 1000ohms and condensers, preferably electrolytic condensers, of more than 6microfarads, said receiver further including, in the lead to one of saidelectrolytic condensers, a signal lamp acting as guard device andlighting in the case of incorrect connection of the receiver with directcurrent mains.

2. A universal receiver operable by connection With either alternatingcurrent or direct current mains, said receiver being provided withsmoothing means consisting of ohmic resistances in the order of 1000ohms and condensers, preferably electrolytic condensers, of more than 6microfarads, said receiver further including, in the lead to one of saidelectrolytic condensers, a signal lamp acting as guard device andlighting in the case of incorrect connection of the receiver with directcurrent mains, the signal lamp being so chosen as to burn out when theincorrect connection continues for a relatively long time.

3. In a universal receiver having a supply circuit adapted to be fedwith current derived either from alternating current mains or fromdirect current mains, smoothing means and a signal lamp in the supplycircuit, said smoothing means consisting of ohmic resistances in theorder of magnitude of 1000 ohms and condensers preferably electrolyticcondensers of more than 6 microfarads and being connected in the leadline between the terminals for the mains supply, said signal lamp beingalso connected in the lead line between said terminals, said lamp actingas a guard device and lighting in the case of incorrect connection ofthe arrangement with the direct current mains.

4. In a universal receiver having a supply circuit adapted to be fedwith current derived either from alternating current mains or fromdirect current mains, smoothing means and a signal lamp in the supplycircuit, said smoothing means consisting of ohmic resistances in theorder of magnitude of 1000 ohms and condensers preferably electrolyticcondensers of more than 6 microfarads and being connected in the leadline between the terminals for the mains supply, said signal lamp beingalso connected in the lead line between said terminals, said lamp actingas a guard device and lighting in the case of incorrect Ill) connectionof the arrangement with the direct current mains, said signal lamp beingso chosen as to burn out when incorrect connection to the direct currentmains continues for a relatively long time.

5. A universal receiver operable by connection With either alternatingcurrent or direct current mains, said receiver being provided withsmoothing means consisting of ohmic resistances and condensers, saidreceiver further including, in the lead to one of said condensers, asignal lamp acting as a guard device and lighting in the case ofincorrect connection of the receiver with the direct current mains.

6. A universal receiver operable by connection with either alternatingcurrent or direct current mains, said receiver being provided withsmoothing means consisting of ohmic resistances and condensers, saidreceiver further including, in the lead to one of said condensers, asignal lamp acting as a guard device and lighting in the case ofincorrect connection of the receiver with the direct current mains, saidsignal lamp being so chosen as to burn out when the incorrect connectioncontinues for a relatively long time.

7. A universal receiver operable by connection with either alternatingor direct current, said receiver having three potential supplyterminals, the first of said terminals being properly connectable to thenegative side of a source of direct current potential, or to one side ofa source of alternating current potential, the second of said terminalsbeing connectable to the other side of said source of alternatingcurrent potential, the third of said terminals being properlyconnectable to the positive side of said source of direct currentpotential, said receiver being provided with smoothing means includingohmic resistances in the order of 1000 ohms and at least oneelectrolytic condenser of more than 6 microfarads, said resistances andcondenser being so connected together that in case of incorrect polingof said source of direct current potential with said first and thirdterminals, at least one of said resistances prevents the destruction ofsaid electrolytic condenser.

8. A universal receiver operable by connection with either alternatingor direct current, said receiver having three potential supplyterminals, the first of said terminals being properly connectable to thenegative side of a source of direct current potential or to one side ofa source of alternating current potential, the second of said terminalsbeing properly connectable to the other side of said source ofalternating current potential, the third of said terminals beingconnectable to the positive side of said source of direct currentpotential, said receiver including a plurality of coupledmulti-electrode vacuum tubes containing anodes and heatable cathodes, arectifier having a heatable filament and an anode potential means, theinput to said rectifier being through said second terminal and aconnection system including all of said means and adapted to beenergized by direct or alternating current, a filter, a resistor, saidfilter being connected through said resistor to the output of saidrectifier, said filter including an electrolytic condenser, andconnections from the filter and anodes of said vacuum tubes, whereby asubstantially constant potential is supplied either from said directcurrent or said alternating current source of potential, the destructionof said electrolytic condenser being prevented in case of incorrectpoling of said source of direct current potential with said first andthird terminals, by said resistance.

PAUL KAPTEYN.

